The present invention relates generally to the field of modulating airfoil lift and more specifically to the use of a pulse detonation actuator (PDA) for injecting fluid into an airfoil boundary layer.
In a wide variety of applications, airfoils are used to create a pressure rise in an ambient fluid flowing over the airfoil. The pressure rise acting over the airfoil surface produces a xe2x80x9clift forcexe2x80x9d or, simply, xe2x80x9clift.xe2x80x9d Examples of airfoils include, but are not limited to, aircraft wings; rotor blades for propellers, fans, compressors, turbines, helicopters, and other rotorcraft; and stator vanes for compressors and turbines.
In operation, an airfoil creates a pressure rise from a suction surface on one side of the airfoil to a pressure surface on an opposite side by imposing on the fluid flow a greater curvature on the suction surface than on the pressure surface. A reduction of the efficacy of the airfoil results, however, when the fluid flow boundary layer separates from the suction surface.
One strategy for reducing the tendency toward boundary layer separation is to inject fluid into the boundary layer through jets in the suction surface. Typically, the effectiveness of this strategy increases as the velocity of the injected fluid approaches the velocity of the bulk fluid flow. Conversely, applicability of the strategy is conventionally limited by the pressure rise and velocity increase for fluid injection producible by conventional means.
A pulse detonation actuator (PDA) provides a means for creating a pressure rise and velocity increase greater, in some applications, than the pressure rise and velocity increase available for boundary layer fluid injection by conventional means. Opportunities exist, therefore, to broaden the applicability of boundary layer fluid injection through the use of PDAs.
The opportunities described above are addressed, in one embodiment of the present invention, by an apparatus comprising: an airfoil adapted for generating a lift force; and a first pulse detonation actuator disposed inside the airfoil and adapted for impulsively detonating a fuel/air mixture to produce a pressure rise and velocity increase of combustion products therein, the airfoil having a plurality of lift control holes adapted for communicating combustion product flows from the first pulse detonation actuator to an airfoil surface to modulate the lift force.